U.S. patent number 5,424,625 [Application Number 08/037,246] was granted by the patent office on 1995-06-13 for repulsion motor.
Invention is credited to Lambert Haner.
United States Patent |
5,424,625 |
Haner |
June 13, 1995 |
Repulsion motor
Abstract
A brushless repulsion motor in which the rotor carries
electronic switch circuits for selectively shorting the rotor
windings at appropriate times in its rotational cycle. A
non-contact reference signal source on the stator enables the
electronic circuitry to operate as desired. The disclosed motor
arrangements are useful as substitutes for conventional brush-type
repulsion motors, universal series motors, synchronous motors,
servomotors and stepping motors.
Inventors: |
Haner; Lambert (Rocky River,
OH) |
Family
ID: |
21893275 |
Appl.
No.: |
08/037,246 |
Filed: |
March 26, 1993 |
Current U.S.
Class: |
318/725; 318/724;
318/400.41 |
Current CPC
Class: |
H02K
29/10 (20130101); H02K 37/00 (20130101); H02P
6/32 (20160201); H02P 6/00 (20130101); H02P
25/102 (20130101); H02P 1/24 (20130101) |
Current International
Class: |
H02P
1/16 (20060101); H02K 29/06 (20060101); H02P
25/10 (20060101); H02P 1/24 (20060101); H02K
29/10 (20060101); H02P 25/02 (20060101); H02K
37/00 (20060101); H02P 6/00 (20060101); H02P
001/24 () |
Field of
Search: |
;318/725,726,696,254,138 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Shoop, Jr.; William M.
Assistant Examiner: Masih; Karen
Claims
I claim:
1. A repulsion motor comprising a stator and a rotor rotatably
mounted on said stator for rotation about an axis, the stator
having at least one pair of poles, a field winding on said stator
for producing a field in said rotor, a plurality of coils on said
rotor adapted to electromagnetically interact with the field of the
stator winding, electronic switching means on said rotor to
selectively short successive ones of its coils when they are in
angular positions relative to said stator poles where the stator
field is effective to induce a current in them and produce a
resultant relative torque and rotation between the rotor and
stator.
2. A motor as set forth in claim 1, wherein the electronic
switching means is responsive to the angular position of the rotor
relative to the stator to short appropriate ones of said rotor
coils.
3. A motor as set forth in claim 1, wherein said electronic
switching means is operated by a non-contact signal source on said
stator.
4. A motor as set forth in claim 1, wherein said electronic
switching means includes sensing means on said rotor that rotates
in a circular path about said axis and is responsive to the
proximity of a reference marker on said stator, said reference
marker having a zone of influence on said sensing means that is a
small fraction of the circular length of the path of said sensing
means.
5. A motor as set forth in claim 4, including means to vary the
effective angular position of said reference marker on said stator
to vary the torque and/or speed developed on said rotor.
6. A repulsion stepping motor comprising a stator and a rotor
rotatably mounted on the stator, the stator having a pair of poles,
a field winding on said stator for producing a magnetic field
between said poles in said rotor, a plurality of coils angularly
distributed about said rotor and adapted to electromagnetically
interact with the field of the stator winding, electronic switch
means on the rotor for selectively shorting said coils, and control
means on said stator for operating said electronic switch means to
align a selected one of said coils with an axis fixed by reference
to the axis of the magnetic field of said poles.
7. A repulsion stepping motor as set forth in claim 6, wherein at
least three angularly spaced coils and three associated electronic
switches are provided on said rotor.
8. A repulsion stepping motor as set forth in claim 7, wherein said
electronic switch means and control means include mutually
non-contacting signalling means.
Description
BACKGROUND OF THE INVENTION
The invention relates to improvements in electric motors and, in
particular, to an improved repulsion-type motor.
PRIOR ART
A conventional repulsion motor is typically constructed with a
single phase stator and a DC rotor with an armature winding
connected to a commutator. Diametrally opposed carbon brushes
riding on the commutator are shorted together but are not connected
directly to the AC line power. When AC power is applied to the
stator winding, currents are induced in the armature to create the
rotor field. Important advantages possessed by the repulsion motor
are relatively high values of starting torque with comparatively
low starting current, ability to sustain high starting torques for
long periods of time such as may exist under conditions of high
inertia loads, and adaptability to wide range speed control.
The speed torque curve of a repulsion motor is similar to that of a
universal series motor or a series-type DC motor. The no-load speed
of the repulsion motor can be many times higher than the
synchronous speed. A major problem with the conventional repulsion
motor from the standpoint of practical application is that the
brushes and commutator wear out quickly because of the arcing and
heat generated by the brushes in contact with the commutator.
Today, basic repulsion motors are not commonly used because of this
serious brush wear problem. Other motor types have been designed to
attempt to minimize these problems. For example, a repulsion start,
induction-run motor is designed with a squirrel cage rotor embedded
in the wound armature. Mechanical means are used to lift the
brushes from the commutator when the rotor speed reaches a
predetermined value and the motor then runs as an induction motor.
This is done to develop a very high starting torque for the
induction motor.
SUMMARY OF THE INVENTION
The invention involves a motor construction that exhibits the
desirable characteristics of a brush-type repulsion motor but
eliminates the conventional brushes of such a motor and their
recognized disadvantages. In accordance with the invention,
electronic switching means is carried on the rotating armature to
short individual coils at appropriate times in a cycle of rotation
to eliminate the need for brush and commutator elements.
In the disclosed embodiments, the electronic switching means is in
the form of power semi-conductors carried on the rotating armature.
More specifically, one electronic switch circuit is provided for
replacing the switch and current carrying function of one pair of
oppositely disposed commutator segments or bars. Any electrical
power needed to energize the electronic switching means and any
related control circuitry on the armature is produced on the
armature by induction from the stator field.
The control electronics on the armature includes means to sense the
angular position of the armature relative to the stator in order to
control the actuation of the electronic switches.
The control circuitry is operative when a coil is at a
predetermined angular position, relative to the stator, to switch
an appropriate electronic switch to short the ends of an associated
coil together. The result of this short is essentially the same as
that achieved in the prior art by a pair of opposed shorted
brushes.
Where the control circuitry on the rotor senses a reference point
associated with the stator, the reference point or marker can be
moved to different angular locations relative to the stator to
change torque, speed and/or direction of the rotor. By
electronically controlling the location of the reference point or
marker to control torque magnitude and direction, a servomotor can
be made. A significant advantage, here, is that a power amplifier
is not necessary since the motor is connected directly to the AC
power line.
In a motor of the disclosed repulsion design, the power electronics
need only control the connections in the armature. Therefore, a
large amount of mechanical power developed by the motor is
controlled with power electronics that is relatively small in power
handling capacity. For example, in terms of power handling
capacity, the power electronics can conceivably be one-fifth to
one-tenth the size of an inverter unit that would be required to
drive a conventional induction motor of equivalent motor power
output. The brushless repulsion motor offers other advantages. For
instance, in conventional practice with an inverter powered motor,
the line power must be rectified and converted to DC power and then
reconverted or "inverted" to control the AC power for the motor.
When the AC line power is rectified with a capacitor input filter,
the line current is not sinusoidal but, rather, is pulsed. This
creates line harmonics and also a different RMS value. This
different form factor and RMS value will heat line fuses
differentially and, generally, the fuse line must be derated by
20-25% of its ampere capacity. With the brushless repulsion motor
of the invention, a double conversion is not necessary and the line
current of the motor is sinusoidal.
Application of the brushless repulsion motor to replace universal
series motors has the additional advantage of not having any
exposed active electrical parts. This means less of an electrical
shock hazard to the user of equipment such as hand tools.
Many other performance advantages and/or features accrue to the
brushless repulsion motor as compared to conventional AC and DC
motor designs. The electronic switch can be designed such that its
opening and closing is modulated by factors other than relative
position between the rotor and stator. This capability allows the
design of special or tailored speed/torque curves. This capability
can also provide for a more efficient conversion of energy on
start-up which lowers start-up currents and thereby eliminates the
need to employ separate electronic: "reduced voltage" start-up
controls found in many industrial applications and which are added
items of expense.
With regard to the use of the brushless repulsion motor as a
servomotor, its performance characteristics are exceptionally good
with respect to dynamic response. With the brushless repulsion
motor, only a part of the total amount of electrical power is
contained in the rotor/armature, therefore the electronics need not
process all of the electrical power. By contrast, in a permanent
magnet DC servomotor known in the art, all of the electrical power
must enter and be processed through the armature by an external
electronic power control or amplifier. The electrical time constant
of the armature is a dominant factor that limits the dynamic
response. In modern high performance AC servos an induction motor
is used with a control algorithm referred to as "flux vector
control" or "field oriented control". All of the electrical power
is supplied by an external power amplifier or inverter and the
control calculates the relative position of the stator field to the
rotor field to provide optimum control response. Here again, the
limitations involve the rotor electrical time constants and the
stator electrical time constants. Also, the torque in the brushless
repulsion motor, is developed by a change in relative position of
the rotor field and stator field. Changing this position requires
only to change an external reference marker position and this can
be done in many ways that are extremely fast. For example,
photodiodes and phototransistors can be used to change the position
of the reference marker. The electrical time constant of the
rotor/armature is also a diminished factor because not all of the
windings are switched at the same time and this creates, in effect,
a reduced time constant.
The principles of the invention can be applied, for example, to a
brushless repulsion motor with universal-series motor
characteristics, to a servomotor, to a synchronous motor and to a
stepping motor.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is diagrammatic axial view of a two-pole repulsion motor
constructed in accordance with the present invention;
FIG. 2 is a diagram of an electronic circuit, in accordance with
the invention, that serves to selectively shunt a typical pair of
opposed commutator segments, or their equivalents for winding
termination, in place of the action of a pair of conventional
electrical brushes, it being understood that one such circuit is
provided for each pair of opposed commutator bars or segments;
FIG. 3 is a schematic diagram of a repulsion motor and related
servo-control circuit in accordance with the invention;
FIG. 4 is a view similar to FIG. 2 showing a different electrical
circuit for each pair of opposed commutator segments.
FIG. 5 is a diagrammatic representation of a repulsion motor useful
as a stepping motor; and
FIG.6 is a diagrammatic view of a portion of the motor of FIG. 5
taken from the view 6--6 indicated in FIG. 5.
DESCRIPTION OF THE PREFERRED EMBODIMENT
An electric motor 10 constructed in accordance with the invention
is diagrammatically illustrated in FIG. 1 in a view looking axially
from an electronic commutator end. The motor device 10 in the
illustrated example is a single-phase two-pole repulsion motor. A
motor stator 11 comprises a pair of diametrally opposed magnetic
poles 12 having field windings 13 that typically are connected to
60 HZ single-phase utility power. The field windings produce a
magnetic field that is in a direction indicated by an imaginary
line or axis 36 extending from one pole 12 to the other. The stator
11 can be constructed in essentially the same manner as is a
conventional universal series motor or a repulsion motor.
A rotor or armature 17 of the motor 10 can be constructed
essentially in the same manner as a conventional universal series
motor with certain exceptions or modifications discussed below. The
rotor is supported for rotation about a central axis 16 by axially
spaced bearings mounted on opposite ends of the stator in a
conventional manner, for example. The rotor 17 has a plurality of
axial or longitudinal slots 18 on its periphery into which are
fitted a plurality of generally longitudinal coils 19. Typically,
the coils 19 have many turns and each slot 18 receives the sides of
more than one coil 19. The coils 19 are terminated on commutator
segments or bars 20 in accordance with conventional practice as
will be understood from the description below. Additionally, the
coils 19 can be terminated in other convenient ways since the
invention eliminates the regular commutating service of the
segments or bars 20. It will be understood from this discussion
that electrical brushes such as are found in conventional repulsion
motors or in universal series motors are eliminated from the
construction of the motor. The motor 10 operates generally like
known repulsion motors except that it includes electronic means on
the rotor 17 to short the ends of the rotor winding coils 19 and
thereby eliminates the need for conventional electrical brushes to
do the same.
The commutator segments or coil terminations 20 are typically
arranged in diametrically opposed pairs and for the purpose of the
explanation of the invention, but not by way of limitation, there
are twelve segments or coil termination points illustrated in
certain of the disclosed constructions. Associated with each pair
of segments 20 is an electronic switch circuit 21 diagrammatically
represented at 21 in FIG. 1 and in component form in FIG. 2. In
elementary terms, it will be understood from the description below
that at appropriate times in the rotation of the rotor 17,
electronic switches will be individually closed or rendered
conductive to short, i.e. electrically connect their respective
segments 20 together. As with conventional repulsion motors, with
the field windings 13 energized and appropriate commutator segments
20 shorted, the effect is to develop torque and rotation between
the rotor 17 and stator 11.
With reference to FIG. 2, a typical electronic switch circuit 21
comprises a pair of power MOSFET transistors 22 and a triggering
device such as a phototransistor 23. The output terminals of the
power transistors 23 are connected individually to the diametrally
opposed segments 20 numbered, clockwise, 1 and 7 while their inputs
are connected in common. The phototransistor 23 and power
transistors 22 are energized by related electronic circuitry
comprising a pair of diodes 28, a capacitor 29, a resistor 31 and a
zener diode 32. The inputs of the diodes 28 are connected to
segments 20, numbered 5 and 9, other than the segments 20 (1 and 7)
associated with the power transistors 22. Since voltages vary
between various armature windings during rotation of the rotor 17,
a voltage (limited by the zener diode 32) is developed on the
capacitor 29 sufficient to operate the phototransistor 23 and power
transistors 22. When the phototransistor 23 is illuminated by a
suitable light source 24, it switches on and, in turn, switches on
the power transistors 22 through their gates placing them in a
conductive state.
The electronic switch 21, with its associated circuitry illustrated
in FIG. 2, is replicated for each pair of segments 20, but for
clarity in the drawings, this replication is not shown. It will be
understood that the electronic switches 21 and related energizing
circuitry for all of the segment pairs 20 are suitably fixed to the
rotor so that the same rotates in unison with the rotor. For heat
transfer or other reasons, the electronic switch components and
related circuitry can be carried on the rotor outside of the stator
by interconnecting the same to the segments 20 with wires that run
along the rotor shaft, in a slot or central hole, through the
associated conventional shaft bearing.
For purposes of explanation, with reference to the embodiment of
FIGS. 1 and 2 and like embodiments, it will be assumed that the
angular extent and relationship, with reference to the axis of
rotation of the rotor 17 of the segments 20 to the armature coils
19 is like that of a conventional repulsion or universal series
motor and, further, that the phototransistors 23 each have a window
or light receptor, in an angular sense, that is centered at a
bisector of the arc of an associated segment 20 and have a field of
view, in the angular sense, generally coextensive with the arcuate
extent of a typical commutator segment 20. That is, the angular
location of each light receiving means for a phototransistor 23 is
at the same angular center as in associated segment 20. In FIG. 2,
the light window or receiving means is shown diagrammatically as a
mirror 33 in a light path 34 to the phototransistor 23. Other
control signal receiving arrangements include prisms, fiber optics
or the direct positioning of the phototransistor 23 at the actual
angularly centered station for receiving a control signal from the
light source 24. In this embodiment, all of the signal receiving
means in the form of mirrors 33 and the light source 24, which is
duplicated at diametrally opposite points, all lie in a common
plane transverse to the axis of rotation of the rotor 17.
Consequently, the circular path or orbit of each signal receiving
mirror means 33 for each set of commutator segments 20 is the same
as that of the others.
The light sources 24 provide a pair of diametrally opposed position
reference markers and are suitably mounted or supported on the
stator 11 at approximately the 2 o'clock and 8 o'clock positions in
the showing of FIG. 2. These reference markers 24, when the
electronic circuit 21 includes a phototransistor 23 or other light
sensitive device, comprise known devices such as a light emitting
diode (LED) or an incandescent bulb powered by the AC line and any
necessary power supply. The position reference markers or light
sources 24 are located so that the light signal or radiation
emitted from them shines in a beam that radially intersects the
path or orbit of the signal receptors or mirrors 33 for the
phototransistors 23. With the stator windings 13 and reference
marker light sources 24 energized, the relevant electronic switch
21, represented by S.sub.3 in FIG. 1 will cause its associated
segments 20 (numbered 3 and 9) to be shorted. This results from the
light of the reference marker 24 energizing the phototransistor 23
to energize the associated power transistors 22.
Analogous to the situation in a conventional repulsion motor, when
a pair of segments 20, in an angular position other than aligned
with a hard neutral axis 36 corresponding to the 12 o'clock/6
o'clock locations or aligned with a soft neutral axis 37
corresponding to 3 o'clock/9 o'clock locations are shorted and the
stator windings k3 are energized with an AC voltage, the rotor 17
will develop a torque and will rotate. In the case illustrated in
FIG. 1, the electronic circuit represented by the symbol S.sub.3 is
activated by the light source 24. In the showing of FIGS. 1 and 2
where the reference marker lights 24 are disposed approximately at
the 2 o'clock and 8 o'clock positions, torque and rotation of the
rotor 17 will be induced in a clockwise direction. As the light
signal receiving mirror 33 associated with the circuit S moves away
from the influence of the reference marker light 24, the signal
receiving mirror 33 of the adjacent circuit S.sub.2 moves into such
influence and rotor rotation is thereby continued. A study of FIG.
1 reveals that each circuit S.sub.i will be energized for shorting
its respective segment pairs 20 twice each revolution--once at each
arrival of the mirror 33 at the diametrally opposed reference
marker light sources 24.
From the foregoing it will be understood that the circuits S.sub.l
-S.sub.6 in combination with the reference marker light sources 24
perform the segment shorting function previously performed by
electric brushes and commutator segments in conventional repulsion
motors.
Like the action in a conventional repulsion motor, where the
angular position of the reference marker lights 24 is moved away
from the 2 o'clock/8 o'clock position counter clockwise towards the
hard neutral axis 36, the torque and speed developed by the motor
generally increases. With the lights 24 very close to hard neutral
axis 36, torque decreases and is zero when centered at this
location. Where the lights 24 are moved clockwise from the 2
o'clock/8 o'clock position past the soft neutral axis 37 to the 4
o'clock/10 o'clock positions, the rotor rotates in the opposite
direction, i.e. counter clockwise with torque and speed increasing
with increasing angular displacement of the brushes from the
neutral axis 37.
The variable torque, speed and directional characteristics of the
repulsion motor of the present invention make it particularly
suited as a servomotor 40. FIG. 3 is a diagrammatic representation
of such a unit. The armature or rotor 17 and stator 11 of the motor
40 are essentially the same as that described in connection with
FIGS. 1 and 2 except for the reference marker or light source
arrangement 24. In the present structure, a plurality of pairs of
diametrally opposed of reference marker light sources 24a-24c,
24x-24z are disclosed circumferentially about the rotor. Typically,
the reference markers 24 all lie in a plane transverse to the axis
of the rotor 17 and common to the signal receivers or mirrors 33.
FIG. 3 illustrates a servocontrol circuit 41 for operating the
motor 40. The speed, direction and angular position of the rotor or
armature shaft is monitored by a transducer 42 that produces a
signal to a servocontroller 43. A speed/position input command
signal is applied to a line 44 to the servocontroller 43. The
servocontroller 43 compares the reference or command signal on the
line 44 with the measured signal from the transducer 42 and
produces a control signal to a reference marker control 45. This
reference marker control 45, in turn, activates an appropriate
diametrally opposite pair of the reference markers 24a, 24b or 24c
and 24x, 24y or 24z to produce a desired rotational direction,
torque and/or speed of the motor rotor 17. It will be understood
that the relative location of the active pair of reference markers
24 determines the speed, torque and direction of the rotor. As
discussed above, the reference markers 24c and 24z closest the hard
neutral axis 37 of the poles 12 generally producing high torque and
speed, when activated, as compared to the reference markers 24a,
24x nearest the soft neutral axis 37. Thus, as the error signal
between the command signal and the feedback transducer signal
increases (in either polarity), the servocontrol will switch to the
next pair of reference marks 24 in the array from the axis 37
towards the pole axis 36. Conversely, as the error signal reduces,
the reference marker control shifts to a pair closer to the axis
37.
A variation in the construction of the servomotor 40 is the
provision of a single pair of reference markers 24 that are
supported for movement about an arc concentric with the rotor and
are mechanically moved by an actuator controlled by the reference
marker control. Other variations in the servomotor are
contemplated. For example, the control of the light emitting diodes
represented by the light sources 24 can be embodied as just the two
pairs at the extreme ends of the arcuate array, i.e. 24c and 24y.
The torque control can be achieved by pulse width modulation of the
current through the LED. When the error signal increases, the LED
is pulsed on for a longer time duration.
FIG. 4 illustrates an electronic switch circuitry 51 that can be
substituted for the electronic switch circuitry for the commutator
pairs in place of the electronic switch circuitry 21 of FIG. 2. It
has been found that the circuitry 51 when used in replication for
circuits S.sub.1 -S.sub.6 of FIG. 1 produces a synchronous motor
50. The circuitry 51 includes a phototriac 52 and an alternistor
53. Specifically, it has been found that the rotor 17 will lock
onto a rotational speed that is an integral multiple of the power
supply frequency. For example, if the supply frequency is the 60 HZ
commercial, power line and the motor is a two pole machine, then
the synchronous speed will be 3600 rpm. If a four pole machine is
constructed, the speed will be 1800 rpm. If the power supply
frequency is adjustable, the synchronous speed will be a fixed,
multiple of that frequency.
The alternistor 53 is composed of two SCR's back-to-back in the
same package. An alternistor has the advantage over a triac when
switching inductive loads in that a snubber network is not usually
required. As shown in FIG. 4, the alternistor 53 has each one of
its conduction electrodes on a commutator segment (e.g. 1, 7) that
is diametrically opposite the other. The phototriac 52 has its
light receiving area schematically designated at 54. Similarly to
the circuit operation described in connection with FIG. 2, the
switch 51 will be activated twice per each revolution of the rotor
where two LEDs or reference markers 24 are provided. When the rotor
17 moves and the phototriac 52 has passed the area of influence of
the LED 24, the switch 51 will remain in conduction until the
current is reduced to near zero or attempts to reverse. This
turn-off is controlled by the voltage induced in the rotor windings
19 presented to the commutator segments or bars 20. The voltage is
determined by the line power and the rotor motion. Because of the
nature of the devices 52, 53, a synchronization mode is created and
the rotor 17 locks into the frequency. A motor provided with the
circuitry of FIG. 4 will run at the synchronous speed as the load
torque increases until a breakdown point. Thereafter, the motor
will run at a speed that is lower than synchronous as the load
torque increases. This motor has the advantage over other kinds of
synchronous motors that operate from a single phase power supply in
that it has a relatively large starting torque. As previously
indicated, there are many ways, moreover, to control the LED light
source 24 to alter the performance curve of the motor.
Reference is now made to FIGS. 5 and 6 where a repulsion motor 60,
using the principles of the invention, is constructed with stepping
motor characteristics. The motor 60 is similar in arrangement to
that described in connection with FIGS. 1 and 2 as it pertains to a
stator 11 and rotor 67. Electronic switches S.sub.1, S.sub.2 and
S.sub.3, such as shown in FIG. 2, are associated with commutator
segments 70 that are spaced 60.degree. apart on the circumference
of the rotor. As before, it will be understood that signal
responsive or sensing devices 76 (such as a light guide or the lens
of a photosensitive device) are angularly centered with respect to
a corresponding commutator bar or segment 70. In this embodiment,
however, each electronic switch S.sub.1 -S.sub.3 has two
diametrically opposed signal sensing devices 76 and the sensing
devices of each electronic: switch S.sub.1, S.sub.2 and S.sub.3
rotate in a separate track or path T.sub.1, T.sub.2 and T.sub.3.
The circumferential tracks or paths T.sub.1 -T.sub.3 of the
individual pairs of sensing devices 76 are axially displaced from
one another as indicated in FIG. 6. For each switch circuits
S.sub.1, S.sub.2 and S.sub.3, and each pair of associated sensing
devices 76, there is a separate energizing light signal source 71,
72 and 73. Each signal source 71-73 extends through an arc of
120.degree. about the circumference of the path of its respective
signal sensing devices 76. Since each circuit S.sub.1 -S.sub.3 has
a pair of diametrically opposed sensing means 76, a signal source
71-73 need only be provided on one side of the rotor or armature.
The signal sources 71-73 are appropriately mounted or fixed
relative to the stator.
Each energizing signal source 71, 72 or 73 is comprised, for
example, of a plurality of discrete LEDs that collectively cover a
full 120.degree. of arc. A study of FIG. 6 shows that in rotation
of the rotor, the sensing devices or photodetectors 76 of each
electronic circuit sweeps in its track T.sub.1, T.sub.2 or T.sub.3
in a path axially aligned with an associated LED array 71, 72 or
73.
In operation, only one light array 71, 72 or 73 is operated or
switched on by a controller 74 at any time. Where the LED array 71
associated with S.sub.1 is activated, the rotor 67 moves to the
position illustrated in FIG. 5 where the associated sensor 76 and
commutator segment 70 is aligned with the neutral axis 37. When the
LED array 72 for S.sub.2 is switched on, S.sub.2 becomes closed or
conductive and the rotor 67 will move to a position where its
sensor 76 is aligned with the neutral axis 37. Then, if the array
72 is turned off, then the array 73 is turned on, the rotor 67 will
move to a position with the S3 sensor 76 in line with the neutral
axis 37. From the foregoing, it will be evident that full rotation
of the rotor 67 or reverse rotation is achieved by repeating or
reversing the cycle of operation of the arrays 71-73. The number
and location of the electrical switches S.sub.1 -S.sub.3 and number
of arrays 71-73 can be varied to meet the demands of a particular
application. The motor 60, or others with similar construction, can
be used in applications where conventional stepping motors are
used.
The repulsion stepping motor 60 can be used as a synchronous
variable speed motor by controlling the rate or frequency by which
the LED array 71-73 are switched on and off. In this case, the
control or amplifier 74 controls the power to the LED arrays 71-73
which may be in the order of milliwatts and the motor 60 can
develop hundreds of watts. In typical present day stepping motors,
all of the motor power passes through the control electronics.
The electronically controlled switch S.sub.i of the various
disclosed embodiments can be implemented in many ways besides those
disclosed that operate with phototransistors or other
photoresponsive devices. Other non-contact devices include Hall
effect transistors that sense a magnetic field that can be produced
by a permanent magnet or an electromagnet that substitutes for a
light source.
While the invention has been shown and described with respect to
particular embodiments thereof, this is for the purpose of
illustration rather than limitation, and other variations and
modifications of the specific embodiments herein shown and
described will be apparent to those skilled in the art all within
the intended spirit and scope of the invention. Accordingly, the
patent is not to be limited in scope and effect to the specific
embodiments herein shown and described nor in any other way that is
inconsistent with the extent to which the progress in the art has
been advanced by the invention. An example of a variation is a
construction where a signal to the electronics for selectively
shorting a coil is developed by a commutator and brush set with the
current through the brushes being essentially limited to that
necessary for an adequate signal.
* * * * *